Setup of MS Outlook 2000 Remote mail

I?d to set up a laptop to use OL2000, It calls to our Ras and links to the Exchange server. It runs when you send an e-mail to any of our local addresses, but when you try to send an e-mail to an Internet one, it says that could not reach that address.
If you connect this laptop with an Ethernet there is no problem, (but is not useful).

Does anyone know any problem using dialup connection to Exchange Server, in Outlook 2000?